This invention relates to the detection of proteins by the utilization of the phenomenum by which such proteins interact specifically either immunologically or nonimmunologically.
Exemplary constructions of diagnostic devices for use in the immunological detection of proteins are disclosed in U.S. Pat. Nos. 3,926,564--Giaever, 4,011,308--Giaever, and 4,018,886--Giaever. An article "Protein Deposition on Field-Emitter Tips and Its Removal By UV Radiation" by Panitz and Giaever [Surface Sci. 97, 25-42 (1980)] describes the removal of protein from the surface of a metal-coated slide by the use of ultraviolet light in order to clean the surface.
The term "biological particle" is intended to encompass smaller proteins (e.g., plasma proteins, antigens, antibodies, lactins) and bodies of proteinaceous material (e.g., viruses, bacteria, cells) capable of stimulating antibody production, when injected into an animal and/or having the property of interacting specifically either immunologically or nonimmunologically.
Immunological reactions are highly specific biochemical reactions in which a first protein (e.g., an antigen) combines (links) with a second protein specific to the first protein (e.g., an antibody) to form an immunologically complexed protein. Immunological reactions taking place within a biological system, such as an animal or human being, are vital in combating disease. In a biological system, the entry of a foreign protein, i.e., an antigen, causes the biological system to produce the antibody proteins specific to the antigen by a process not fully understood at this time. The antibody protein molecules have available chemical combining or binding sites, which complement those of the antigen molecule, so that the antigen and antibody chemically link or bond to form an immunological complex protein.
Most antigens are proteins, or contain proteins as an essential part, whereas all antibodies are proteins. Proteins are large molecules of high molecular weight, i.e., they are polymers consisting of chains of various numbers of amino acids. A typical proteinaceous material will comprise multiple entities (e.g., protein molecules, cells, etc.), which do not adhere to each other. Therefore, when a proteinaceous material is brought into contact with a substrate, it deposites as a single layer. If the entities are molecular in size, this resulting single layer is monomolecular; if the entities are larger, the layer will be a thicker single layer. No other arbitrary protein will adhere to a deposited protein layer. On the other hand, specifically reacting protein to a protein adsorbed onto the substrate will immunologically bond thereto.
In accordance with the teachings in the above-cited patents, this phenomenum is exploited to provide medical diagnostic apparatus in which a substrate (e.g., a glass slide, the surface of which has been provided with a layer of metal, such as indium) having a first layer of one protein adsorbed thereon is used to test suspected solutions for the presence of the protein specific thereto (i.e. the protein specifically reacting therewith). If the specifically reacting protein is present in the solution, the substrate after exposure to the solution will have a double protein layer thereon. If the specifically reacting protein is absent from the solution, the slide after exposure to the solution will have only the original layer thereon. Optical, electrical, chemical and tagged-detection means for distinguishing between the presence of double and single protein layers are known in the art and in the aforementioned patents.
Because antibodies are produced by biological systems in response to invasions thereof by foreign proteins, the detection of antibodies in a biological system is of medical diagnostic value in determining the antigens to which the system has been exposed. A typical example of diagnostic detection of antibodies is the detection of antibodies to syphilis or gonorrhea in blood serum. Conversely, the detection of certain antigens in a biological system also has medical diagnostic value; examples of diagnostic detection of antigens include the detection of HCG protein molecules in urine as a test for pregnancy, and detection of hepatitus-associated-antigen (HAA) molecules in the blood of prospective blood donors.
In order to perform such diagnostic tests, the appropriate protein of the immunologically reacting pair must be obtained. The only known source of an antibody protein is a living biological system. More particularly, only vertebrates are known at this time to exhibit immunological reactions to the introduction of a foreign protein. For example, many antibodies are found in the blood serum of animals and human beings which have been exposed to the corresponding antigens. Many antigens, however, may be controllably produced in laboratory cultures. However, some antigens, for example, HAA molecules are at present like antibodies, only obtainable from the higher living biological systems.
It is known in the immunological art that antibody molecules function as antigens when introduced into the system of a vertebrate to whom they are foreign proteins. Accordingly, specifically reacting antibodies to a given antibody may readily be produced in such vertebrate system.
While emphasis herein for the purposes of exemplification will be on immunologically reactive biological particles (the simplest case being the antigen-antibody pair), it should be understood as explained at the onset that this invention is equally useful with sets of biological particles that undergo forms of biological interaction other than the immunologic reaction, the only criterion being that the particles must be mutually specific.